The Discovery of Longitude

It was known long before their sufficient refinement, that accurate clocks could be used to measure longitude with corresponding accuracy. John Harrison's chronometers were the first able to keep time on a ship within acceptable limits for measuring its position. The requirement is to have Greenwich Meantime available on board for comparison with local time.

This work describes position-keeping in navigation, the absence of methods for determining longitude, and hence the effect of the invention of the marine chronometer in the eighteenth century.

To navigate around this site, please use the imagemap to the left by clicking on the topic of your choice, or alternatively by clicking the "NEXT" button at the bottom of each page to work your way through the entire document. Many of the pictures at the top of each document are "clickable" and will take you to larger images of the same thing with some further information